NASA's Mars Odyssey Shifting Orbit for Extended Mission

PASADENA, Calif. -- The longest-serving of six spacecraft now
studying Mars is up to new tricks for a third two-year extension
of its mission to examine the most Earthlike of known foreign planets.

NASA's Mars Odyssey is altering its orbit to gain even better
sensitivity for its infrared mapping of Martian minerals. During
the mission extension through September 2010, it will also point
its camera with more flexibility than it has ever used before.
Odyssey reached Mars in 2001.

The orbit adjustment will allow Odyssey's Thermal Emission Imaging
System to look down at sites when it's mid-afternoon, rather than
late afternoon. The multipurpose camera will take advantage of the
infrared radiation emitted by the warmer rocks to provide clues to
the rocks' identities.

"This will allow us to do much more sensitive detection and mapping
of minerals," said Odyssey Project Scientist Jeffrey Plaut of NASA's
Jet Propulsion Laboratory, Pasadena, Calif.

The mission's orbit design before now used a compromise between what
works best for the Thermal Emission Imaging System and what works best
for another instrument, the Gamma Ray Spectrometer.

On commands from its operations team at JPL and at Denver-based Lockheed
Martin Space Systems, Odyssey fired thrusters for nearly 6 minutes on
Sept. 30, the final day of the mission's second two-year extension.

"This was our biggest maneuver since 2002, and it went well," said JPL's
Gaylon McSmith, Odyssey mission manager. "The spacecraft is in good
health. The propellant supply is adequate for operating through at
least 2015."

Odyssey's orbit is synchronized with the sun. The local solar time has
been about 5 p.m. at whatever spot on Mars Odyssey flew over as it made
its dozen daily passes from between the north pole region to the south
pole region for the past five years. (Likewise, the local time has been
about 5 a.m. under the track of the spacecraft during the south-to-north
leg of each orbit.)

The push imparted by the Sept. 30 maneuver will gradually change that
synchronization over the next year or so. Its effect is that the time of
day on the ground when Odyssey is overhead is now getting earlier by about
20 seconds per day. A follow-up maneuver, probably in late 2009 when the
overpass time is between 2:30 and 3:00 p.m., will end the progression
toward earlier times.

While aiding performance of the Thermal Emission Imaging System, the
shift to mid-afternoon is expected to stop the use of one of three
instruments in Odyssey's Gamma Ray Spectrometer suite. The suite's
gamma ray detector needs a later-hour orbit to avoid overheating of a
critical component. The suite's neutron spectrometer and high-energy
neutron detector are expected to keep operating.

The Gamma Ray Spectrometer provided dramatic discoveries of water-ice
near the surface throughout much of high-latitude Mars, the impetus for
NASA's Phoenix Mars Lander mission. The gamma ray detector has also
mapped global distribution of many elements, such as iron, silicon and
potassium, a high science priority for the first and second extensions
of the Odyssey mission. A panel of planetary scientists assembled by
NASA recommended this year that Odyssey make the orbit adjustment to
get the best science return from the mission in coming years.

Increased sensitivity for identifying surface minerals is a key science
goal for the mission extension beginning this month. Also, the Odyssey
team plans to begin occasionally aiming the camera away from the straight-down
pointing that has been used throughout the mission. This will allow the
team to fill in some gaps in earlier mapping and also create some stereo,
three-dimensional imaging.

Odyssey will continue providing crucial support for Mars surface missions
as well as conducting its own investigations. It has relayed to Earth nearly
all data returned from NASA rovers Spirit and Opportunity. It shares with NASA's
Mars Reconnaissance Orbiter the relay role for Phoenix. It has made targeted
observations for evaluating candidate landing sites.

Mars Odyssey, launched in 2001, is managed by JPL, a division of the
California Institute of Technology, Pasadena, for NASA's Science Mission
Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime
contractor for the project and built the spacecraft. Investigators at Arizona
State University, Tempe, operate the Thermal Emission Imaging System. Investigators
at the University of Arizona, Tucson, head operation of the Gamma Ray Spectrometer.
Additional science partners are located at the Russian Aviation and Space Agency,
which provided the high-energy neutron detector, and at Los Alamos National
Laboratories, New Mexico, which provided the neutron spectrometer.